1. Field of the Invention
The present invention relates to titanium oxide particles useful for pigments, catalysts, catalyst supports, adsorbents and the like, and more particularly, to titanium oxide particles having a high specific surface area useful for deodorants adsorbing obnoxious gases such as ammonia, mercaptans, hydrogen sulfide and aldehydes as well as for scavengers capable of removing noxious materials by decomposing them through photocatalytic reaction.
2. Description of Related Art
Obnoxious gases widely produced in inhabitant environments include ammonia, methyl mercaptan, hydrogen sulfide, trimethylamine, methyl sulfide, and acetaldehyde. An attempt has been made to remove these obnoxious gases allowing maintenance of pleasant inhabitant environments, for example, techniques of removing odor by adsorbing obnoxious gases on activated carbon or impregnated activated carbon containing acids or alkalis have been employed. However, these activated carbons are black and so limitted in their application. For example, when the activated carbons are incorporated in sanitary products such as paper diapers and sanitary napkins which come into direct contact with the skins of human beings, such treatments as not rendering the products black in color to have a clean feel to the products are required, or when the activated carbons are to be incorporated in interior wall sheets, decorations and cosmetics, the products are difficult to impart a desired color so that they are applied to only black products. Moreover, there are problems that the activated carbons has specifically a low ability in deodorization of ammonia and a reduced performance in removing obnoxious gases if they adsorb first moisture.
On the other hand, there have been marketed a variety of adsobents, for example, white ones capable of imparting a clean feel to the products as well as coloring them in desired tinge such as silica gel, zeolite, activated alumina and activated terra abla. However, these white adsorbents have a low deodorizability to the aforementioned obnoxious gases so that they can not be substituted for activated carbons.
As one of the white deodorants, there have been proposed particles having a firmly bonded structure produced with zinc oxide, titanium dioxide and water as disclosed in Japanese Patent Publication (Post-Exam.) No. Hei 3-33022.
According to the disclosure of this patent, the white deodorants can be produced by preparing a mixed aqueous solution of a water soluble titanium compound and a soluble zinc compound and an alkaline aqueous solution, and combining both the solutions to achieve a pH in the range of 6 to 11 of the mixed solution, thereby effecting neutralization to produce a precipitate comprising zinc oxide, titanium dioxide and water, form which solid particles having a firmly bonded structure of a uniform composition are subsequently formed. In this method, the concentrations of the starting materials such as a titanium compound and the like and the velocity of combining both the solutions must be precisely controlled rendering the operation complicated. In addition, when the pH of the combined solution shifts to outside the defined range, the resultant white deodorant has poor characteristics as disclosed in Japanese Patent Publication (Post-Exam.) No. Hei 3-33022. Moreover, the precipitate produced by the neutralization is in a gel state which tends to be difficult to filtrate, and when dried, the particles of the precipitate may coagulate so firmly that it is difficult to pulverize. Thus, there remain many things to be improved.